Former Windows chief Steven Sinofsky has kept busy since leaving Microsoft. After jumping into his new role at venture capital firm Andreessen Horowitz and joining the board of auto-sharing company Local Motion, the tech heavyweight has now signed on as an official advisor to cloud storage and collaboration service Box.

In his new role with Box, Sinofsky will "lend his experience and insights to help the company advance its platform strategies and organizations to the next level," Box co-founder and CEO Aaron Levie, wrote in a blog post.

Levie said he first reached out to Sinofsky about six months ago via an "unsolicited Facebook message," and the relationship grew from there.

"Steven has a stronger and more fluid vision for the future of computing than almost anyone I've met," Levie wrote. "As we kept talking and sometimes meeting over Pho, I realized we had to get him involved with Box."

He added that the former Microsoft executive has "spent much of his career thinking about technology transformations, navigating them, and — in many cases — helping to drive them. We're very excited to have him advising us as we hopefully bring the next generation of tools to the next billion workers."

For his part, Sinofsky said in a Facebook post that he's "looking forward to having fun and working with the team at Box."

Levie has been critical of Sinofsky's former employers in the past, arguing that Microsoft has failed to innovate and released applications that don't actually solve users' problems.

"What we've seen is a complete lack of innovation from Microsoft and Oracle, because when you don't have competition, you have no need to constantly drive performance improvements, functionality, and innovation, and that's what's happened," Levie said in a 2011 interview with PCMag.